1. Field of the Invention
The present invention relates to electronic components and, more particularly, to an electronic component including an external electrode.
2. Description of the Related Art
In a wiring board in which an external electrode is formed on a substrate body made of, for example, resin or ceramics, it is necessary to ensure the adhesion strength of the external electrode on the substrate body so that the external electrode is not detached from the substrate body after the wiring board is mounted.
For example, in a multilayer substrate 100 shown in a cross-sectional view in FIG. 9, the surface roughness of a surface that is in contact with a substrate body 110 made of resin of each external electrode 121 that is externally exposed on the front and rear surfaces of the substrate body 110 is set to a value higher than the surface roughness of the internal electrode pattern. Accordingly, the anchor effect for the substrate body 110 is increased to improve the adhesion strength of the external electrode 121 (for example, refer to Japanese Unexamined Patent Application Publication No. 2006-344828).
However, since the surfaces of copper foils each having a thickness of 35 μm are roughened by, for example, surface treatment to be used as the external electrodes in this multilayer substrate, the surface roughness in the multilayer substrate is not so great. Particularly, when the external electrodes are reduced in size, the external electrodes may not have a sufficient adhesion strength with the multilayer substrate. In addition, since the surfaces of the copper foils are uniformly roughened by the surface treatment or the like, the external electrodes have a direction that is weak in an impact applied from, for example, a side surface of the multilayer substrate mounted on a printed circuit board or the like due to the shapes of the electrodes and the chips, and the improvement effect of the adhesion strength against the impact from the direction is reduced.